When faced with a decision, ask yourself, 'does this bring me closer to God?"
Or does it distract you from him? If it is going to distract you, chances are, it is sin.
That is my simple litmus test. And I have to say, I have yet to encounter a situation that wasn't clear. It is not a matter or morals or concience, or even scripture. Just- how does this affect my relationship with God? Does it enhance it or detract from it?
When I am faced with any kind of temptation, small or large, seemingly sinful or not, I ask that question and it clears the matter up for me.